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How Much Granular Manganese Dioxide?


Foxden

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Thanks, the slip is a great alternative but wouldn't work in my situation. I was surprised by 5%, I was thinking more like 1% since that's about the amount of granular Illmenite I use in a speckled glaze I make. Testing is simple enough but I was hoping to avoid it.

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I was going to press some slabs into a mold with some detail which would be lost if coated with slip. I understand the toxicity of the fumes from manganese and always wondered why manufacturers used it in clay bodies.

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I had a project requiring a slab with a "white" surface, but did not want to use porcelain for the main body - I was using a groggy cone 10 stoneware.  I made slabs and then brushed a thin layer of porcelain over the slab (both sides) and when the slip became soft leather hard (still flexible), I compressed the surface with a rib and repeated the slip applications until I was sure the layer was thick enough to allow the surface decoration to be completed. The decoration was done with stamps and carving.

 

My point is that a laminated substrate made with a "clean" clay body coated with a "doctored" surface layer will work even in press molded if you work out a sequence of steps before you start.

 

You could make a slip with your clay body adding "something" to produce dark specks (not necessarily manganese) and apply the slip before pressing step with the result being  crisp impressions and dark specks.

 

LT

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The wonderful thing about working with clay is that there are multiple ways to do things. I generally prefer the simplest. I can buy Highwater's Speckled Brownstone, but just thought I would wedge the same granular manganese that they do into some plain Brownstone clay. And yes, I am working with this project in cone 6, oxidation. At cone 10 I, too, get all the speckles I need from the iron in my clay body.

 

Thanks.

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I have used crushed bisque soaked in red iron oxide "stain" and sun-dried as an "accent" to press into slab surfaces.  (Think Jerry Rothman sky-pot type stuff.)  The bisque dust was easy to make with a box, a block anvil, and a hammer.  I screen it with stretched open weave cloth over a kitchen sieve.

Something similar might work well here also. 

 

LT

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I have used basalt granules instead of manganese to speckle my white clay body. i have used 20-40 mesh grains in a concentration between 2 - 4 %. It is not toxic and gives a nice cookie and cream appearance.... just a thought.  It also doesn't play too badly with any glazing.

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Hmmm- lots of good ideas here.  I'll have to mark this page somehow. I wonder how a slip made out of some speckled cone 9-10 stoneware would fare at cone 6 oxidation (electric)?

I am making some cone 6 mugs that require a white slip for a mocha pattern. I tried this white slip at cone 9 (with the mocha pattern) and I really like how the spots came thru the white slip, plus the dry look of the slipped surface (I only glazed the lip and interior).

 

So, what if I have some cone 6 mugs, dipped in cone 9 speckled-clay-slip, then another dip in my white slip, then my mocha pattern, then a bit of clear glaze inside? How do I prevent the cracking while drying all this slip? Just dip fast and use thin coats?  I'll need to set up a little production line for all the ingredients.

 

Good ideas!

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Iron oxide is refractory in oxidation firings, certainly to cone 6. It generally adds colors to glazes and clay bodies. In reduction, it's a different story, it changes form due to the lack of oxygen and acts as a flux. Sometimes bubbling up from the clay through the glaze giving rise to the familiar speckles at cone 10.

 

I have been trying to get that look in oxidation and am experimenting with suggestions offered to me from others on the forum.

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Personally, I would not add granular manganese to a clay body because it is toxic. Consider that. Also when firing,

do not be around the fumes. Manganese can enter the body through skin contact , inhalation, and ingestion.

Handle with care.

Marcia

 

Not to crack open a can of worms but my understanding is that manganese isnt water soluble so I'm told it cannot be absorbed through skin.

 

This was told to me after I lost my sh!t after seeing my Casius Basaltic clay had 1.5% manganese in it and I pretty much went ham at the shop that sold it to me without any sort of warning.  They assured me that it 100% cannot be absorbed through skin and the clay in wet is form totally non-toxic providing you dont get any in your mouth/lungs.

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Personally, I would not add granular manganese to a clay body because it is toxic. Consider that. Also when firing,

do not be around the fumes. Manganese can enter the body through skin contact , inhalation, and ingestion.

Handle with care.

Marcia

 

Not to crack open a can of worms but my understanding is that manganese isnt water soluble so I'm told it cannot be absorbed through skin.

 

This was told to me after I lost my sh!t after seeing my Casius Basaltic clay had 1.5% manganese in it and I pretty much went ham at the shop that sold it to me without any sort of warning.  They assured me that it 100% cannot be absorbed through skin and the clay in wet is form totally non-toxic providing you dont get any in your mouth/lungs.

 

http://www.ceramicstoday.com/articles/080999.htm

 

http://community.ceramicartsdaily.org/topic/7487-manganese-dioxide/

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Personally, I would not add granular manganese to a clay body because it is toxic. Consider that. Also when firing,

do not be around the fumes. Manganese can enter the body through skin contact , inhalation, and ingestion.

Handle with care.

Marcia

 

Not to crack open a can of worms but my understanding is that manganese isnt water soluble so I'm told it cannot be absorbed through skin.

 

This was told to me after I lost my sh!t after seeing my Casius Basaltic clay had 1.5% manganese in it and I pretty much went ham at the shop that sold it to me without any sort of warning.  They assured me that it 100% cannot be absorbed through skin and the clay in wet is form totally non-toxic providing you dont get any in your mouth/lungs.

 

http://www.ceramicstoday.com/articles/080999.htm

 

http://community.ceramicartsdaily.org/topic/7487-manganese-dioxide/

 

 

 

I dont want this to be taken confrontationally, but your first source says exactly what I said:

 

"Manganese compounds used by potters are inorganic, like manganese dioxide, oxide and manganese carbonate; they do not penetrate the body via the skin"

 

 

...and your second link shows you directly contradicting it:

 

"Yes, manganese dioxide is toxic -- both in dry form (breathing risk) and in suspended form (it can be absorbed by through the skin, causing neurological problems)."

 

 

JBaymore's comment seems to back up the sources I've spoken with, that the real threat here is from the fumes generated during firing.

 

Again, seriously, I'm not trying to be some mouthy internet know it all. 

 

What none of these articles touch on is range of sensitivity among different people.  I spent about 5 or 6 days firing manganese clay (cassius basaltic) in a not-so-well ventilated area.  It _wrecked_ me.  Sleep problems, headaches, hallucinations, it was very severe and scary, and I believe personally believe that episode was caused by manganese fumes.

 

So I did a lot of research because I'm scared sh!tless that I've done perm damage to myself, is where I'm going here, but a chemist I am not.  So I'm a bit of a stickler for getting to the truth on this subject, not someone just looking for arguments.  I hope that shows through, and I appreciate you chiming in obviously (I hope).

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Guest JBaymore

The documented potential issues with manganese are via inhalation.  Manganese in clay bodies potentially increases your risks in two areas;  the respirable "fines" from the clay body DRY dust that invariable accumulates in the studio (the granules are not an issue) and mainly the fume that comes off the kiln in the firing.  A "fume" is not a "gas"... but is an ultra-fine, sub-micron "dust" particle.  VERY respirable and stays in the air a long time.

 

Then add the concepts of intensity, duration, and frequency to the equation concerning your possible "exposure".

 

This is not simple stuff.  That is why god created scientists, toxicologists, occupational health specialists, and ventilation engineers. ;)   There are only (to my knowledge) anecdotal individual pieces of information about potters getting manganese poisoning.  There are medically documented studies showing instances of industrial workers getting manganese poisoning.  They are NOT the same thing.  The industrial studies point to the potential risks...... but are not 100% applicable to what it is we do.  No one in the medical field has studied the impacts on studio potters (to my knowledge).   So we 'extrapolate' from the available info, and do the best we can.

 

Are we right to be concerned about the potential health impacts?  Of course.  Should we 'seal ourselves in giant baggies' to go thru life?  I think not.

 

Education, education, education.  The information about health and safety in the studio environment is out there.  Then you have to assess if you are a "glass half full" or a "glass half empty" type of person in your approach to life.

 

One of the important things that I tell people in my ceramic toxicology sessions and workshops...... if you have a health concern that you think is related to what you do in the studio, go get a referral from your primary care physician to an occupational health specialist.  The average GP type doctor is not typically trained to think about things the way that you need them to approach the subject.  Take a list of the materials that you use, and the MSDSs for them with you to both of your doctors. 

 

A lot of GPs will be surprised that you work with some of the stuff that you do.  If they KNOW about it, they will keep a little reminder in their head when they deal with your general health issues over the years.

 

best,

 

................john

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  • 2 months later...

I read both the links stated above, yet many of the comments seem to have conflicting information. I would like to know the answers to questions I have not seen answered.

 

So after researching this subject, can one really assume manganese dioxide when fired and glazed over with the speckles showing through is food safe? Can one drink or eat off of its surface for years and not be harmed? That is the question not being answered through my findings. All I have come across is the largest health impact is if breathed as a dust or fume. So while the potter may have adverse affects from creating the pot, will the average consumer have a reaction?

 

Another question I have is iron oxide dust/filings food safe when glazed over or left unglazed on funcationalware? While most people do not have bad reactions to this metal, when fired and glazed the same as manganese dioxide, is it safe to eat off of? My only concern is the rust of it being exposed (should a part of the piece not be glazed).

 

Any input? (:

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